How to test a used laptop before you buy it

Test a used laptop in front of the seller, before you pay. The checks below take about 15 minutes; most run in the laptop’s own browser, so open this page on it.

Before you start

• Ask the seller to have it charged and signed in, with its own charger.
• Bring wired earbuds, a USB drive or your phone and its cable for the ports, and your phone for a Wi-Fi hotspot.
• Meet somewhere you can shade the screen; bleed and clouding hide in daylight.

Look it over first

About 2 minutes, with the laptop still off.

1. Check the case for cracks, dents and missing screws or feet. Scratched screw heads suggest it has been opened; ask what was repaired.
2. Set it on a flat table. A bulging bottom, a raised touchpad or a lid that no longer closes flat can mean a swollen battery, which is a safety risk. Walk away.
3. Open and close the lid a few times. The hinges should move evenly and hold the screen at any angle, with no cracks where they meet the case.
4. Under a light, check the screen for scratches and for marks left by the keys pressing against it.

Check the screen

About 4 minutes. Wipe the screen with a dry cloth first, because dust looks like a faulty pixel.

1. Open the Monitor Test, press Start test and step through the colors. Check the whole panel, edges included, for a tint on white, dark bands or patches.
2. In the Dead Pixel Test, turn on Auto cycle and scan the screen section by section. A dot that stays black on every color is dead, one that stays one color is stuck, and one that stays bright on black is hot. No software repairs a dead pixel, so count them before you agree on a price.
3. Shade the screen and view the black and near-black levels of the Backlight Bleed Test. Glow that shifts as you move your head is IPS glow, which is normal; bright patches that stay put at the edges are bleed. Skip this on an OLED screen, which has no backlight.
4. On the gray field of the Screen Uniformity Test, look for cloudy patches, pressure marks and dark corners.
5. With a white or gray field showing, move the lid slowly through its range. Flicker, lines or a picture that cuts out at some angles can point to a worn display cable in the hinge.

For what counts as a defect, and how to run a laptop’s built-in screen test, see how to test a new monitor.

Test the keyboard and touchpad

About 3 minutes.

1. Open the Keyboard Test, press Start test and press every key. Each key turns solid while held, then tinted; one that stays solid after you let go is stuck. Open Keys not yet tested to see what is left; keys the laptop lacks, such as Pause, stay there.
2. Type a sentence in any text box and look for doubled or missing letters.
3. Fn and some system keys normally never reach a web page, so try them directly: brightness, volume and the keyboard backlight, if it has one.
4. Open the Mouse Test and move a finger across the whole touchpad. The trail should follow smoothly, without jumps.
5. Click, right-click, then scroll with two fingers up, down and sideways. The Left clicks, Right clicks and Scroll counts should rise with each.
6. On a touch screen, press Start test in the Touch Screen Test and drag a finger over every cell to find dead zones.

Test the speakers, microphone and webcam

About 2 minutes.

1. Disconnect headphones and Bluetooth audio, open the Speaker Test and press Left, then Right, with your ear near each side. Turn the volume up for a moment and listen for rattles or crackling.
2. If there is a headphone jack, plug in your earbuds and press Left and Right again.
3. Open the Microphone Test, press Start test and allow access. The meter should rise when you speak and fall back when you stop. To hear how it sounds, record a few seconds with the Mic Test with Playback.
4. Open the Webcam Test and press Start camera. The picture should appear in focus, and any camera light should come on. A black picture usually means a closed privacy shutter, or a camera key or switch that is off.

If the browser blocks either device, see how to allow camera and microphone access.

Check Wi-Fi, ports, charger and fan

About 2 minutes.

1. If this page loaded over Wi-Fi, the Wi-Fi works; if not, connect to your phone’s hotspot. Turn on Bluetooth and check that it finds your phone.
2. Plug your USB drive or phone into each USB port and check that it shows up or starts charging.
3. Plug in the charger and check that the battery icon shows it charging. If it charges over USB-C, try each USB-C port; some models charge through only some.
4. Check the charger cable for fraying or tape. Its printed output should match the maker’s rating for the model.
5. Listen to the fan as you work. Silence under light load is normal; grinding or rattling is not.

Check battery health

About 1 minute. No web page can read battery wear, so use the operating system.

Windows

1. Search Start for Terminal or Command Prompt and open it.
2. Type powercfg /batteryreport and press Enter. Windows saves a report called battery-report.html in the current folder and shows its path (Microsoft’s reference).
3. Open the report. Under Installed batteries, divide Full charge capacity by Design capacity to see the share of the original capacity left. The cycle count is there too, if the battery reports it.

Mac

1. Choose Apple menu > System Settings, then Battery. Battery Health reads Normal, or Service Recommended when the battery holds less charge than when it was new. On many models, the Info button next to it shows the maximum capacity.
2. For the cycle count, hold Option, choose Apple menu > System Information, then Power. Apple lists the rated maximum for each model in Determine battery cycle count for Mac laptops.

Confirm the model and accounts

About 1 minute.

1. Open Device Info. It shows the system, browser, screen resolution, CPU cores and, in Chromium-based browsers, a rounded memory figure, which can expose a listing that overstates the cores. No web page can read the model, serial number, processor name or storage size.
2. Find those in the system. On Windows, Settings > System > About lists the processor and installed RAM, and Settings > System > Storage the drive. The System Information app lists the System Model, and Get-CimInstance Win32_BIOS in PowerShell shows the SerialNumber. On a Mac, About This Mac in the Apple menu shows the model name, chip or processor, memory and serial number, and System Settings > General > Storage the drive.
3. Compare that serial number with the label on the underside, if there is one. If they differ, ask why. A maker’s warranty-check page, where one exists, can confirm the model and remaining coverage.
4. Ask the seller to remove their accounts before you pay. On a Mac with Apple silicon or a T2 chip, Activation Lock stays on while Find My is on, so they need to turn off Find My. On Windows, Settings > Accounts > Access work or school should be empty; an entry can mean an organization still manages the laptop. A password prompt before the system starts is usually a firmware password, which the seller should remove.

What a browser can and cannot check

Check	In the browser	Not in the browser
Screen	Pixel faults, bleed and uneven areas, judged by eye	Brightness in nits, color accuracy, panel type
Keyboard	Which keys register and which stick	Fn and keys the system takes first
Touchpad	Tracking, clicks and scrolling	Three- and four-finger system gestures
Speakers and microphone	Each side plays; the mic picks up sound	Measured sound quality
Webcam	A live picture, its resolution and frame rate	Whether the camera light works
Battery	Nothing about wear	Health and cycle count
Identity	System, screen, CPU cores, rounded memory	Model, serial number, processor name, storage

A private sale often has no returns, so ask about anything that fails before you pay, and price it in.